At the end of Overdose, Grave speaks one and only one line—to Mika. Going by the game's storyline, it's probably the first time she's ever heard him speak. He really does care about her. D'aww.
The ending of the anime. "...Welcome home."
Part of the ending of the first game, in which Grave survives the ordeal and leaves with Mika, having found a new purpose/reason to "live" again.
"...I believe you."
In episode 23 Bear Walken dissolved the Overkills before going off to confront Brandon. He told them that they are free to do what they want. Then in next episode, A bunch of them arrived to save Harry and Sherry from an assassination because they felt that it was Bear's deepest desire to make sure that his daughter and her husband is safe.
The reason why Bear let his men go? He didn't want them to be converted into Orgmen. That's rather sweet for a guy like Bear.
The relationship between Grave and Mika. She's a living memento of the people he knew and loved when he was Brandon, and he's more or less her big brother, a father figure, and a best friend who gives his all to keep her safe. Even with almost all of his memories gone, he still managed to hold on to at least one—a promise he made to Maria.
A small one from the first game: during the intermission before the final level, Mika manages to contact Grave by use of a 2-way radio. She's relieved to know that Grave is fine after the explosion, and says that she's more than a little scared to be alone, but she has complete faith in him. She says she'll wait for him to return and wishes him luck in completing his final objective.